Day-693 | Daily MCQs | UPSC Prelims | ENVIRONMENT

Answer: B
Explanation
Option B is correct.
A new study has shown that bumblebees pick up new ‘trends’ in their behaviour by watching and learning from other bees, and that one form of a behaviour can spread rapidly through a colony even when a different version gets discovered. The research (PLOS Biology) provides strong evidence that social learning drives the spread of bumblebee behaviour — in this case, precisely how they forage for food.
A variety of experiments were set up to establish this. The researchers designed a two-option puzzle box that could be opened either by pushing a red tab clockwise or a blue tab counter-clockwise to reveal a 50 percent sucrose solution reward. ‘Demonstrator’ bees were trained to use either the red or blue tabs, with ‘observer’ bees watching.
When it was the observers’ turn to tackle the puzzle, they overwhelmingly and repeatedly chose to use the same method that they had seen, even after discovering the alternative option. This preference for the taught option was maintained by whole colonies of bees, with a mean of 98.6% of box openings made using the taught method.

Answer. D
Explanation:
Charles Darwin carried out several interesting studies on the Galapagos Islands, what amazed Darwin most was the extensive variety of finches on these islands. These species of finches differed from each other with respect to the shape of their beaks and their overall size. These finches, also known as Darwin’s finches, demonstrated the concept of adaptive radiation. It is a type of evolution in which species in the same geographic area, derived from a common ancestor, successfully adapt themselves to their natural environment due to natural selection.
Adaptive radiation is of two types: adaptive divergence and adaptive convergence.
In adaptive divergence, animals of the same or closely related group exhibit great divergence in their morphology when found in a different habitat. For example, the finches of the Galapagos Islands. These finches had originally come from the South American mainland to the Galapagos Islands. With the passage of time, they multiplied and began to compete with each other for food. As a result, all the food resources on the islands were used to the optimum. To take advantage of all the available food sources on the islands, the finches adapted themselves to the different varieties of food. One observable trait that pointed to this adaptation was the altered beaks of different species of finches. Their beaks divided them into specialised insectivorous and vegetarian varieties respectively.
Another type of adaptive radiation is adaptive convergence, where animals of unrelated groups occupying the same habitat exhibit common features. For example, Australian marsupials such as the kangaroo, marsupial rat, banded anteater, tiger cat, Tasmanian wolf and Koala.
Marsupial mammals are characterised by their pouch in which the female carries the young through the initial days of infancy. On tracing the evolution of these marsupials, it was found that the drifting of the continents had shaped their history. When the ancient land masses of Laurasia and Gondwana broke apart to form separate continents, the marsupials were also divided into two groups. While one group of marsupials was isolated on the Australian island, the other group remained in South America. Thereafter, the marsupials on both these continents evolved in a parallel manner and hence this is also known as parallel evolution.
Interestingly, on comparing marsupials and placental mammals of Australia, we find similar adaptive radiations between them. Although they have separate lineages, they resemble each other physically. Studies show that the impelling causes of adaptive radiation are the need for food, safety and for better breeding grounds. Thus, the process of adaptive radiation illustrates how life forms have modified and evolved into new forms.

Answer. A
Explanation:
The scientists from the Wildlife Institute of India (WII) have found that the clouded leopard in western Assam’s Manas National Park and Tiger Reserve seems to play a mysterious game of hide-and-seek in the tropical canopy forests.
It has the largest canines in proportion to its skull size among all cat species. It also has rotating rear ankles that enable it to climb down head first from trees, unlike the other felines.
The researchers also observed that the cat with cloud-like spots on its hide does not follow any specific pattern of operating in a certain space, unlike other carnivores.
They seemed to go wherever they pleased without worrying about other predators, primarily because of their ability to climb trees, even hang upside down from large branches.
The smallest of the big cats, the arboreal clouded leopard’s long tail helps it balance on trees and jump 4 to 6 metres, from one tree to another. The clouded leopard thrives in forested habitat, but a decline of such forests has led to a decline in its count.

Answer. A
Explanation:
The correct sequence of food chain here is:
Diatoms-copepod-shrimp-isopod
● Diatoms are photosynthetic algae (phytoplankton) having a siliceous skeleton and found in almost every aquatic environment including fresh and marine waters, soil, in fact almost everywhere moist.
● Copepods are examples of zooplankton that are key components of marine food chains. They are the most important herbivores in the sea, filtering phytoplankton such as diatoms/dinoflagellates using a sophisticated ‘fling and clap’ technique to grasp the tiny phytoplankton.
● Some species of shrimp such as cherry shrimp are known to feed on copepods as they’re a perfect source of essential vitamins, proteins, and lipids.
● Isopods, also known as woodlice or roly-polies, are fascinating creatures that belong to the crustacean family. These small, armoured critters can be found in various terrestrial habitats around the world, from rainforests to deserts. From fallen leaves and decaying plants to faecal materials, isopods eat anything and everything in the environment. As isopods live on decaying matter, they’re often called detritivores.
● The marine isopods live around 1600 ft deep in the sea or oceans. Their main food is tiny fishes, crabs, shrimp, and other tiny creatures.

Answer. B
Explanation:
Direct seeding is a crop establishment system wherein rice seeds are sown directly into the field, as opposed to the traditional method of growing seedlings in a nursery, then transplanting into flooded fields. Direct seeded rice is seen to be one of the most efficient, sustainable, and economically-viable rice production systems used today. Compared to the conventional puddled transplanted rice (PTR) method prevalent in Asia, DSR delivers faster planting and maturing, conserves scarce resources like water and labour, is more conducive to mechanization, and reduces emissions of greenhouse gases (like methane) that contribute to climate change.
Statement 1 is correct: Direct-seeded rice (DSR) supported by conservation agriculture (CA)-based crop management practices such as zero-tillage, is perceived to address the challenge of producing more rice grain with less water. DSR is endowed with multiple benefits/advantages over transplanted puddled rice (TPR) through savings in labour (40–45%), savings in water (30–40%), fuel/energy (60–70%), and reductions in greenhouse gas emissions.
Statement 2 is correct: In DSR, the absence of stagnant water (as seen in traditional flooded rice fields) and the lack of a head start for rice seedlings create favourable conditions for weed growth. Weed competition remains critical up to 41 days after sowing.
Statement 3 is incorrect: Methane emissions are significantly lower than transplanted puddled rice. Methane emissions can be cut by 40% to 90%, as per researchers.

Advantages of DSR
• No significant reduction of yield under optimal conditions
• Savings on irrigation water by up to 35-40% under efficient water management practices
• Reduces labour and drudgery by eliminating seedling uprooting and transplanting
• Reduces cultivation time, energy, and cost
• No plant stress from transplanting
• Faster maturation of crops
• Lower GHG emissions
• Mechanized DSR provides employment opportunities for youth through service provision business model
• Increases total income by reducing cost of cultivation

Disadvantages/concerns associated with DSR
• Higher seed rates
• Seeds exposed to birds and pests
• Weed management
• Higher risk of lodging
• Risk of poor or non-uniform crop establishment